Rocket firing relay



June 19, 1962 s..1. GRILLO ETAL 3,039,363

ROCKET FIRING RELAY Filed Jan. 28, 1960 United Patented June 19, 1962.Cree

3,039,363 RCKET FIRING RELAY Salvatore J. Grillo, New Britain, andWilliam B. Walker, Hatboro, Pa., assignors to the United States ofAmerica as represented by the Secretary of the Navy Filed Jan. 28, 1960,Ser. No. 5,321 3 Claims. (Cl. 89-1.7) (Granted under Title 35, U.S. Code(1952), sec. 266) The invention described herein may be manufactured andused by or for the Government of the United States of America Iforgovernmental purposes Without the payment of any royalties thereon ortherefor.

'Ihis invention relates to an electric ignition circuit and relay forfiring a rocket and more particularly to an electric ignition circuitand relay 'for ring a rocket by maintaining a detonating chargeelectrically isolated until a prescribed instant of launching.

Electrically ignited rockets red from a launcher present a hazardouspossibility of premature ring due to an undesirable electrical currentappearing in the ignition circuit. This current is primarily caused bystray currents conductively leaking into the circuit from adjacentelectrical `gear or by induction occurring when the circuit is in afield of electromagnetic energy such as emitted by radar transmittersand other high Ifrequency radio transmitters. In applications where therockets are to be tired from vehicles, such as -an airplane, thelaunchers are necessarily located outboard of the vehicle. The rocketsmust therefore be pre-loaded and electrically armed for remote actuationat a later time. Remote electrical actuation often entails longconductor leads yfrom the rocket launcher to a remote actuating deviceand hence obviously multiplies many times the hazard of prematureiiring. A larger area is exposed to conductive leakage and also'theaccompanying antenna eifect of the conductor leads are such as mayproduce a stray or an induced current suicient in magnitude to ignite ahighly sensitive electrically responsive ydetonating charge in therocket.

Various methods and `devices have been contrived for safeguardingagainst premature ring of rockets of the character described. One ofsuch devices consists of using high frequency filters and luy-passes.Complete attenuation of all frequencies, as may be induced byelectromagnetic waves, is diicult and requires a complex electricalnetwork; moreover, the network cannot discriminate between a real:signal and an identical false signal induced or conducted from anexternal source. Another device short-circuits the electrical leads.Obviously, a positive short is required in order to assure no voltagedrop is applied across the detonating charge. Being a temporaryconnection, the likelihood of always having a positive short isseriously diminished. Furthermore, the short-circuiting device must belocated at the rocket, hence additional means for removing the device isrequired. Each of these electrical devices still involves dangerouslylong leads continuously connected between the detonating charge and -aremotely located initiating device. Coupling the last-mentioned factwith the disadvantages of the particular device selected simply returnsthe hazard of premature rocket firing to its original gravity.

The main concept upon which the present invention is premised resides inattaining an ignition circuit which permits the loading of a rocket inthe launcher and the arming of the detonating charge for remoteactuation thereof and which further maintains the charge electricallyisolated frorn the ignition circuit until the prescribed instant ofrocket launching. The general purpose of this invention is to provide ameans for obtaining electrical isolation of the detonating charge Ifromthe ignition circuit at a point in close proximity to the rocketlauncher and which embraces all of the advantages of the similarlyemployed iilter, by-pass and short-circuit type ignition circuits andpossesses none of the aforementioned disadvantages. To attain this, thepresent invention contemplates a relay and shield mounted on the rocketlauncher whereby the electrical leads connected to the detonatorterminate at the rocket launcher and remain electrically isolated fromthe ignition circuit until a prescribed instant of ring. Hence, thedistance of the actuating switch from the launcher is immaterial.

It is an object of the present invention to provide a novel rocketfiring circuit for electrically isolating the leads connected to anelectrically responsive detonating charge at the launcher to diminishthe possibility of premature firing.

Another object of the invention is the provision of a novel rocketfiring relay responsive to remote actuation and adapted to be mounted ina launcher for maintaining short electrical leads connected to anelectrically responsive detonating charge.

A further object of the invention is directed to providing a uniqueelectromechanical relay for selectively and irrevocably connecting acircuit.

Still another object of the invention is to provide an improved andeconomical relay of simplified design.

These and other objects and many of the attendant advantages of thepresent invention will be readily appreciated as the same become betterunderstood -by reference to the Afollowing detailed description whenconsidered in connection with the accompanying drawing, wherein:

FIG. l is a fragmentary longitudinal sectional view of the `breech endportion of a rocket launcher showing in partial eros-section the aft endportion of a rocket and a rocket tiring relay positioned in the launcherfor tiring;

FIG. 2 represents an end View of the rocket firing relay taken along theline 2-2 in FIG. l; and

FIG. 3 is a schematic diagram of the ignition circuit -of the rocketshown in FIG. l.

Referring now to the drawing, wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is illustrated in FIG. 1 the breech end portion of a barrel 10 ofa rocket launcher having an end llange 11. The aft end portion of arocket indicated generally by the numeral 12 is illustrated by apropellant tube 13 andpfour nozzles 14 alternately spaced with fourstabilizing iins 16. The fins 16 are urged toward a spreading position4'about pivots 17 on nozzles 14 by iin ractuator 18 having a piston 19subjected to gas pressures generated in the tube 13.

The tube 13 is connected to the nozzles 14 by retaining ring 21 andincludes a rnain propellant 22 ignited by an ignition charge 23 which inturn is detonated by a primer 24. The primer 24 includes an electric hotWire 26 embedded in a pyrotechnic pellet 27. The wire 26 is grounded atone end to propellant tube 13 by conductor 28 and is connected byinsulated conductor 31 at the other end to a contact button 29 which isalso insulated from the ground. The nozzles 14 include a cement-likesealant 32 that is expelled by gas pressure in tube 13. The button 29 isretained in the position shown by notches 33 in the tins 16, hence thebutton 29 is released when the iins 16 spread outwardly. i

While the drawing shows a rocket with some specicity in order to showtheenvironment of the rocket tiring relay, it will be readily understoodthat any suitable soli'dor liquid-propellant type rocket may he used inconnection with the present invention. v

A rocket iiring relay indicated generally lby the numeral 34 iscomprised of a non-conductive insert 36 and a nonconductive housing 37secured on opposite sides of a metal shield 38 by countersunk screws 40.Insert 36 and housing 37 are preferably fabricated of a phenolic 3 resinmaterial. The shield 38 affords complete isolation of conductors 28 and31 from any electromagnetic waves present around the launcher area. Therelay 34 is inserted in tube 13 until shield 38 positively contactsflange 11. The contact is maintained by detents 39.

A spring-actuated plunger 41 is centrally ldisposed in the insert 36 formaking electrical contact with the button 29. A bifurcated contact 42fixed to the housing 37 is connected to plunger 41 by an insulatedconductor 43. A cover plate 44 encloses the housing 37.

As best seen in FIG. 2, the contact 42 is positioned in housing 37 forengaging contact spring 46 which is xed to housing 37 by screw fasteners47. The spring 46 is connected to an electrical resistance-type heater48 which in turn is connected to one end of a current limiting resistor49, the other end being grounded on shielded cable 51. An insulatedconductor 52 of cable 5l provides an electric ignition signal from anelectrical power source 53 through a manual switch 54, as shown in FIG.3. The cable 51 terminates in a jack 56 for convenient electricalconnection.

The heater 48 is fixed to housing 37 by lugs 57 and a loop of thread 58around the heater 48 restrains spring 46 in stressed position out ofengagement with the contact 42. The thread 58 is of a readily fusiblematerial which breaks when a sufficient current is passed through heater48.

FIG. 3 schematically illustrates the manner in which the relay 34 ofFIGS. 1 and 2 is connected in the ignition circuit for tiring therocket. The electric power source 53, the manual switch 54, the contact42 and the primer 24 are arranged in series, while heater 48 andresistor 49 are arranged in parallel with the contact 42 and primer 24.The current limiting resistor 49 assures that a major portion of thecurrent at terminals A and B appears in the circuit branch containingprimer 24.

The firing operation of a rocket will now lbe summa- Iized. The rocket12 and` relay 34 are inserted into the launcher barrel in the respectivepositions shown and the ignition circuit is armed by connecting theshielded cable 51 to the electrical power source and the manual switch54. The spring contact 46 is held in an open position by the thread 58.Closing the manual switch 54 energizes the heater 48 and fuses thethread 48 until it Ibreaks and releases the contact spring 46. 'Ihespring contact 46 strikes and engages contact 42 whereby the primer 24is energized. It is contemplated that a relatively strong electricalsignal is required to fuse thread 58 thereby precluding the possibilityof heater 48 being sufficiently energized by an undesirable electricalsignal caused by stray currents due to leakage or induced currents dueto surrounding electromagnetic waves.

It is contemplated that the exposure area of contact 42 be very small inrelation to the distance between contact 42 and contact spring 46whereby Contact 42 remains completely isolated from the externalignition circuit until a prescribed instant of ring the rocket 12. Itshould thus be apparent that contact 42 and a small portion of conductor43 are the only ungrounded ele'ctrical elements which are continuouslyconnected to primer 24. In this manner the possibility of an undesirableelectrical signal appearing at primer 24 and resulting in prematureignition is practically eliminated.

It should be understood,` of course, that the foregoing disclosurerelates only to a preferred embodiment of the invention and thatnumerous modiiications and variations may be made therein withoutdeparting from the spirit and scope of the invention as set forth in theappended claims.

What is claimed is:

1. For an electrically tired rocket having its ignition conductorextending from within to an electrical terminal fixed at its read-end,the combination comprising: an electrically grounded launching tubeformed for sliding said rocket endwise therein, a metallic electricalshielding plate having its inner face abutting and covering the breechend opening of said launching tube for grounding any radiation-inducedelectrical signals, a yieldable electrical contact carried on the innerface of said plate and aligned to operably connect with said terminal,force-exerting means carried by said plate and operable on saidyieldable contact to obtain an electrical connection between saidyieldable contact and said terminal when said rocket is positioned insaid launching turbe for firing, a stationary electrical contact iixedwith respect to said plate electrically connected to said yieldablecontact and having only a small portion exposed at the outer face ofsaid plate, a movable electrical contact carried on the outer face ofsaid plate and aligned to selectively engage said portion, forceexertingmeans carried by said plate and operable on said movable contact to movesaid movable contact into engagement with said portion when it isunopposed, rigid heater means lixed to said plate and electricallyconnected between said movable contact and ground, a fusible linkconnected between said heater and said second-named force-exerting meansoperable to selectively maintain said movable contact a relatively largedistance awayV from said portion and to oppose said force-exertingmeans, detent means carried by said plate for yieldably maintaining ahigh pressu-re connection between said inner face of said plate and thebreech end opening of said launching tube; whereby, when the movablecontact and said heater means are connected to the ungrounded terminalof a remotely located power supply, the other terminal of the powersupply being grounded, said heater will generate suflicient thermalenergy to fracture said fusible link and said movable contact will bepropelled into engagement with said portion of said stationary contactthereby providing an electrical signal to the ignition conductorsufficient to lire said rocket from said launching tube.

2. For an electrically tired rocket having its ignition conductorextending from within to an electrical terminal mixed at its rear-end,the combination comprising: an electrically grounded launching tubeformed `for sliding said rocket endwise therein, a metallic electricalshielding plate having its inner face abutting and covering the Ibreechend opening of said launching tube for grounding any radiation-inducedelectrical signals, a relatively small stationary electrical contactcarried on the outer face of said plate, conductor means connected tosaid stationary contact but not exposed to the outer face of said plateand extending through said plate for connection to said terminal when-said rocket is positioned Iin said launching tube, a movable electricalcontact carried on the outer :face of said plate and raligned toselectively engage said stationary contact, vtorce-exerting meanscarried by said plate and operable on said movable contact to move saidmovable contact into engagement with said stationary contact, when it isunopposed, rigid heater means lixed to said plate :and electricallyconnected between said movable contact and ground, a fusible linkconnected between said heater and said force-exerting means operable toselectively maintain said movable contact a relatively large distanceaway from said stationary contact and to oppose said force-exertingmeans; whereby, when the movable contact vand said heater means areconnected to the ungrounded terminal of -a remotely located powersupply, the `other terminal of the power supply being grounded, saidheater will generate sufficient thermal energy to fracture said fusiblelink, and said movable contact will be propelled into engagement withsaid stationary contact thereby providing an electrical signal to theignition conductor sufficient to lire said rocket from said launchingtube.

3. For an electrically tired rocket having its ignition conductorextending from within to an electrical terminal at its rear-end, thecombination comprising: an electrically grounded launching tube formedfor sliding said rocket endwise therein, a metallic electrical shieldingplate having its inner face enclosing the breech end opening of saidlaunching tube for grounding :any radiationinduced electrical signals, arelatively isolated electrical contact iixed in said plate having arelatively small portion at one end exposed on the outer face of. saidplate and the other end formed for connection to said terminal when saidrocket is positioned in said launching tube, a movable electricalcontact carried on the outer face of said plate and :aligned toIselectively engage said one end, iiorce-exerting means carried by saidplate Iand operable on said movable contact to move said movable contactinto engagement with said one end when it is unopposed, rigid heatermeans fixed to said plate and electrically connected between saidmovable contact and ground, a 'fusible link connected .between saidheater and said force-exerting means operable to selectively maintainsaid movable contact a relatively large distance away from saidstationary 10 said launching tube.

References Cited in the file of this patent UNITED STATES PATENTS 152,798,492 Sage et al May 28, 1957 2,821,139 Apstein etal Ian. 28, 19582,832,265 Reid `et al Apr. 29, 1958

